.container {
  width: 800px;
  height: 600px;
  margin: 100px auto;
  border: 1px solid black;
  position: relative;
}
.messageList {
  width: 80%;
  height: 61.8%;
  position: absolute;
  top: 0;
  left: 0;
}
.inputbox {
  width: 80%;
  height: 38.2%;
  position: absolute;
  bottom: 0;
  left: 0;
  box-sizing: border-box;
  border-top: 1px solid #333333;
}
.inputbox > textarea {
  width: 100%;
  height: 80%;
  margin: 0;
  padding: 10px;
  border: none;
  resize: none;
  box-sizing: border-box;
  position: absolute;
  top: 0;
  left: 0;
}
.inputbox > .btns {
  width: 100%;
  height: 20%;
  position: absolute;
  bottom: 0;
  left: 0;
}
.inputbox > .btns > button {
  float: right;
  margin-left: 10px;
  margin-top: 5px;
}
.userlist {
  width: 20%;
  height: 100%;
  position: absolute;
  top: 0;
  right: 0;
  box-sizing: border-box;
  border-left: 1px solid #333333;
}